With 100 deaths per day, the US is experiencing its worst drug overdose epidemic of all time. Drug overdose deaths are the leading cause of injury-related fatality in the US as of 2008, the majority of which are from prescription drugs. Despite this, tools for prevention of emergency medical consequences from drug overdose are lacking. Although substance abusers are typically young with little cardiovascular medical co-morbidity, adverse cardiovascular events comprise a large portion of the morbidity that leads to mortality from drug overdose. Novel clinical prediction tools are needed to individualize prevention strategies to curtail the rise in overdose fatality. This proposal builds upon preliminary data involving over 2,000 patients with drug overdose seeking emergency department (ED) care at an urban hospital network. To advance the field of prevention of medical consequences of drug abuse, proposed is a prospective cohort study of ED overdose patients with these specific aims: (1) Evaluation of high-risk genetic polymorphisms that are predictive of drug overdose fatality; (2) Evaluation of serum biomarkers that predict tissue/organ injury from drug toxicity; and (3) Prospective validation of a previously derived clinical risk tool in the Toxicology Investigators' Consortium (TOXIC), a robust registry of over 70 hospital centers with bedside medical toxicology evaluation of ED overdose patients. In order to achieve these aims, investigators will conduct a prospective observational study among ED patients >18 years old with suspected acute drug overdose enrolled into the TOXIC Registry. Aims 1 and 2 will focus on the subset of TOXIC enrollees at the PI's site (Mount Sinai Hospital in Manhattan, Elmhurst Hospital Center in Queens, NYC Poison Control Center), while the data collection and analysis for Aim 3 will involve the full nation-wide 70-hospital Registry. Genetic screening (Aim 1) and serum biomarkers (Aim 2) will assess for drug overdose vulnerability and prognosis, respectively. A clinical risk score to prevent adverse cardiovascular events will be validated with calculation of diagnostic test characteristics on a widely generalizable population (Aim 3). This proposal's evaluation of genetic screening, serum biomarkers of tissue/organ injury, and a clinical prediction rule, will together fundamentally advance the prevention of medical consequences of drug abuse by providing new tools to risk stratify for drug overdose susceptibility, overdose mortality, and in-hospital adverse events.